Commenting rather than answering because I don't meet all your criteria.
I have had a FMP subscription since 2016, their record collections are very good, I find their search process much better than some other sites and results are more likely to actually be for the person I am researching than either FS or Ancestry.
Having said that I find their 'trees' very clunky', and complicated to add either people or records.
I have a very basic tree on the site and have yet to find anything new on other members trees that involve the same families.
'uses WikiTree Sourcer to transfer a profile from 'FmP' to Wikitree'.
No, and wouldn't even think about it- if I was going to transfer profiles from one site to WT, I would use Ancestry-my own extensive tree because I trust it- and perhaps profiles on FS that I have contributed to and know the profiles are accurate.
FMP records are their strength, not the trees, that I feel were only added because subscribers seemed to want that option.
